JP6838452B2 - Drive device and image forming device - Google Patents

Description

The present invention relates to a drive device and an image forming device.

In an image forming apparatus such as an electrophotographic printer, a transport roller for transporting paper is driven by a stepping motor. According to the stepping motor, accurate speed / position control can be performed with a simple control configuration.

By the way, in recent years, as the speed of the image forming apparatus has increased, it has been required to shorten the acceleration time of the transport roller and increase the target speed. However, in the general-purpose stepping motor used in the image forming apparatus, the output torque is insufficient, so that step-out occurs and the transport roller cannot be accelerated in a short time. Further, when an expensive stepping motor with high torque is used, it is necessary to constantly flow an excessive current in order to secure a torque margin, which causes a problem that power consumption increases.

In connection with this, Patent Document 1 below states that the output of the brushless motor is coupled to the output of the stepping motor at startup to generate torque in the drive train on the stepping motor side by the brushless motor, and then the constant speed rotation is performed. At times, the technology driven by a stepping motor is disclosed.

Japanese Unexamined Patent Publication No. 2006-017988

However, although the output torque is improved in the above technique, there is a problem that the controllability is not sufficient because the output of the brushless motor can be simply coupled to the output of the stepping motor via the one-way mechanism. No consideration is given to reducing power consumption.

The present invention has been made in view of the above-mentioned problems. Therefore, an object of the present invention is to provide a drive device and an image forming device that have both good acceleration at start-up when driving a drive shaft such as a transfer roller and reduction of power consumption.

The above object of the present invention is achieved by the following means.

(1) Stepping motor and
Brushless motor and
A first power transmission unit that transmits the power of the stepping motor to the drive shaft, and a first power transmission unit that can switch between a connected state in which power is transmitted to the drive shaft and a release state in which transmission is released.
A second power transmission unit that transmits the power of the brushless motor to the drive shaft,
The stepping motor, the brushless motor, and a control unit that controls the first power transmission unit and controls the transmission of power to the drive shaft are provided.
In the first operation phase in which the control unit accelerates the rotation of the drive shaft to a predetermined speed, the control unit transmits the power of both the stepping motor and the brushless motor to drive the drive shaft.
After the first operation phase, in the second operation phase in which the drive shaft is rotated at a constant speed at the predetermined speed, the power transmission of the stepping motor by the first power transmission unit is canceled, and the brushless motor alone is used. A drive device that drives a drive shaft.

(2) In the third operation phase of decelerating the rotation of the drive shaft, the control unit maintains a state in which the power transmission of the stepping motor is released, and controls the brushless motor to decelerate and stop the motor. The drive device according to (1) above.

(3) The second power transmission unit can be switched between a connected state in which the power of the brushless motor is transmitted to the drive shaft and a release state in which the transmission is released.
In the third operation phase of decelerating the rotation of the drive shaft, the control unit switches the power transmission of the stepping motor to the connected state and switches the power transmission of the brushless motor to the released state before the start of deceleration. After that, the drive device according to (1) above, which decelerates and stops by controlling the stepping motor.

(4) The first power transmission unit has a gear moving mechanism for moving at least one gear among a plurality of gears constituting a clutch or a gear train for transmitting the power of the stepping motor to the drive shaft. Then, the transmission of the power of the stepping motor to the drive shaft is switched to the connected state or the disengaged state by the clutch or the gear moving mechanism, from the above (1) to the above (3). The drive device described.

(5) The second power transmission unit has a gear moving mechanism for moving at least one gear among a plurality of gears constituting a clutch or a gear train for transmitting the power of the stepping motor to the drive shaft. The drive device according to (3) above, wherein the clutch or the gear moving mechanism switches the transmission of the power of the brushless motor to the drive shaft between the connected state and the disengaged state.

(6) The control unit is in the first operation phase.
After setting the current value of the stepping motor in the stopped state to the holding current value and generating the holding torque in the stepping motor, the control value of the brushless motor is set to a predetermined value, and the brushless motor holds the holding torque. Generates a torque smaller than the torque,
After that, the stepping motor is accelerated according to a predetermined acceleration curve to keep the control value of the brushless motor constant, or the control value is increased according to the rotation speed of the stepping motor, from the above (1). The drive device according to any one of (5) above.

(7) An image forming apparatus having the driving device according to any one of the above (1) to (6).

(8) The image forming apparatus according to (7) above, wherein the drive shaft is a drive shaft of a transport roller for transporting paper or a drive shaft for driving a crimping separation mechanism of the transport roller.

According to the present invention, since the drive shaft is driven by using the power of the stepping motor and the brushless motor at the time of starting, the output torque is improved and the drive shaft can be accelerated in a short time. In addition, during constant speed rotation after acceleration, the drive transmission of the stepping motor is released, and the drive shaft is rotated only by the brushless motor. This makes it possible to reduce the power consumption during constant speed rotation.

It is sectional drawing which shows the schematic structure of the image forming apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows the schematic structure of the drive device which concerns on 1st Embodiment. It is a block diagram which shows the control system of a drive device. It is a flowchart which shows the procedure of the drive control executed by the control part. It is a figure which shows the subroutine of step S101 of FIG. It is a timing chart for demonstrating the operation of a stepping motor and a brushless motor. It is a timing chart for demonstrating the operation of the stepping motor and the brushless motor in the 1st operation phase. It is a schematic diagram which shows the schematic structure of the drive device which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the drive control in 2nd Embodiment. It is a timing chart for demonstrating the operation of a stepping motor and a brushless motor. It is a schematic diagram which shows the schematic structure of the drive device which concerns on a modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 100 includes a control unit 110, a storage unit 120, an image reading unit 130, an image forming unit 140, a fixing unit 150, a paper feeding unit 160, and a paper conveying unit 170.

The control unit 110 is a CPU (Central Processing Unit), and controls each of the above units and performs various arithmetic processes according to a program.

The storage unit 120 stores a ROM (Read Only Memory) that stores various programs and various data in advance, a RAM (Random Access Memory) that temporarily stores programs and data as a work area, and various programs and various data. It consists of a hard disk, etc.

The image reading unit 130 includes a light source such as a fluorescent lamp and an image sensor such as a CCD (Charge Coupled Device) image sensor. The image reading unit 130 irradiates a document set at a predetermined reading position with light from a light source, photoelectrically converts the reflected light with an image sensor, and generates image data from the electric signal.

The image forming unit 140 includes development units 141Y to 141K corresponding to toners of each color of Y (yellow), M (magenta), C (cyan), and K (black). The toner images formed through the processes of charging, exposure, and development by the developing units 141Y to 141K are sequentially superimposed on the intermediate transfer belt 142 and transferred onto the paper S by the secondary transfer roller 143.

The fixing portion 150 includes a heating roller and a pressure roller, and heats and pressurizes the paper S conveyed to the fixing nips of both rollers to melt and fix the toner image on the paper S on the surface thereof.

The paper feed unit 160 includes a plurality of paper feed trays 161 and 162, and feeds the paper S contained in the paper feed trays 161 and 162 one by one to the transport path on the downstream side.

The paper transport unit 170 includes a plurality of transport rollers 171 for transporting the paper S, and transports the paper S between the image forming unit 140, the fixing unit 150, and the paper feeding unit 160. All or part of the plurality of transfer rollers 171 are driven by the drive device 200 (see FIG. 2).

The image forming apparatus 100 may include components other than the above-mentioned components, or may not include some of the above-mentioned components.

Next, the driving device 200 for driving the transport roller 171 will be described with reference to FIGS. 2 and 3.

FIG. 2 is a schematic diagram showing a schematic configuration of the drive device 200, and FIG. 3 is a block diagram showing a control system of the drive device 200.

2 (a) and 2 (b) are diagrams showing the drive device 200 in the connected state and the disengaged state, respectively. As shown in FIG. 2, the drive device 200 transmits power to the drive shaft a71 to which the transfer roller 171 to be operated is fixed, and drives the drive device 200 to rotate. The drive device 200 includes a stepping motor 210, a brushless motor 220, a first power transmission unit 230, and a second power transmission unit 240. The stepping motor 210 and the brushless motor 220 are provided with rotating shafts a1 and a2, respectively.

The first power transmission unit 230 transmits the power of the stepping motor 210 to the drive shaft a71, and the second power transmission unit 240 transmits the power of the brushless motor 220 to the same drive shaft a71.

The first power transmission unit 230 includes gears 231 and 232, 233, 234, a rotating shaft a3, and a gear moving mechanism 235. The most upstream gear 231 of the gear train is provided on the rotation shaft a1 of the stepping motor 210, and the most downstream gear 234 is fixed to one end side of the drive shaft a71. In the connected state shown in FIG. 2A, the first power transmission unit 230 transmits the power of the stepping motor 210 to the drive shaft a71 in the order of the gear 231 and the gear 232, the rotary shaft a3, the gear 233, and the gear 234. ..

The gear moving mechanism 235 includes a cam, a drive source for moving the cam, and the like (neither of them is shown), functions as a disconnection mechanism, and provides a rotating shaft a3 and gears 232 and 233 fixed to the rotating shaft a3. Move in the direction away from other gears or in the opposite direction. FIG. 2B shows a release state. In this disengaged state, the gear moving mechanism 235 disengages the gear train of the first power transmission unit 230.

The second power transmission unit 240 includes a gear 241 fixed to the other end side of the drive shaft a71. The rotating shaft a2 of the brushless motor 220 is provided with teeth, and the rotating shaft a2 of the brushless motor 220 meshes with the gear 241. The power of the brushless motor 220 is transmitted to the drive shaft a71 via the gear 241 as the second power transmission unit 240.

As shown in FIG. 3, the control unit 110 of the image forming apparatus 100 controls the operations of the stepping motor 210, the brushless motor 220, and the gear moving mechanism 235 (and the gear moving mechanism 245 described later).

The control unit 110 drives the stepping motor 210 by open loop control. The control unit 110 controls the rotation speed of the stepping motor 210 by transmitting a clock signal (CLK) to the driver 211 for the stepping motor 210 and setting the operating frequency of the stepping motor 210. Further, the control unit 110 controls the torque generated in the stepping motor 210 by transmitting a set current signal to the driver 211 for the stepping motor 210 and setting the current value of the stepping motor 210.

Further, the control unit 110 drives the brushless motor 220 under PWM (Pulse Width Modulation) control. The control unit 110 controls the rotation speed and torque of the brushless motor 220 by transmitting a PWM signal to the built-in driver 221 of the brushless motor 220 and setting a control value (duty command value) of the brushless motor 220. Further, the control unit 110 executes speed feedback control of the brushless motor 220 by receiving a rotation speed signal from the built-in encoder 222 of the brushless motor 220.

(Drive control)
Next, the drive control of the drive device 200 for driving the transfer roller 171 according to the first embodiment will be described with reference to FIGS. 4 and 5.

FIG. 4 is a flowchart showing a drive control procedure executed by the control unit 110. This drive control is started, for example, when the image forming apparatus 100 receives a print job. In the drive control, the drive shaft a71 of the stopped transport roller 171 is accelerated to a predetermined speed (target speed) according to a predetermined acceleration curve, rotates at a constant speed at the target speed, and then decelerates according to a predetermined deceleration curve. The algorithm shown by the flowcharts of FIGS. 4 and 5 is stored as a program in the storage unit 120 and executed by the control unit 110.

First, the control unit 110 starts driving the same drive shaft a71 with both the stepping motor 210 and the brushless motor 220 (S101 (first operation phase)). In step S101, the control unit 110 gradually increases the operating frequency of the stepping motor 210 so that the rotation speed increases according to a predetermined acceleration curve by the control shown below.

(Subroutine in step S101)
FIG. 5 is a diagram showing a subroutine in step S101. As the first process, the control unit 110 sets the current value of the stepping motor 210 to the holding current value (S201). More specifically, the control unit 110 sets the current value of the stepping motor 210 to the holding current value, and generates the holding torque in the stepping motor 210 in the stopped state.

Next, the control unit 110 sets the control value of the brushless motor 220 to a predetermined value (S202). More specifically, the control unit 110 sets the duty command value of the brushless motor 220 to a predetermined value, and causes the brushless motor 220 to generate a torque smaller than the holding torque of the stepping motor 210.

Next, the control unit 110 accelerates the stepping motor 210 (S203). More specifically, the control unit 110 gradually increases the operating frequency of the stepping motor 210 so that the rotation speed increases according to a predetermined acceleration curve.

The control unit 110 increases the control value of the brushless motor 220 (S204). More specifically, the control unit 110 increases the duty command value set in the process shown in step S102 in accordance with the increase in the rotation speed of the stepping motor 210. Then, while continuing the processing of steps S203 and S204, the process returns to the processing of FIG. 4 (return).

Returning to the description of FIG. The control unit 110 determines whether or not the rotation speed of the drive shaft a71 has reached the target speed (S102). This determination is made, for example, by comparing the command operating frequency to the stepping motor 210 with the target value. When it is determined that the stepping motor 210 has not reached the target speed (S102: NO), the control unit 110 waits until the stepping motor 210 reaches the target speed.

When it is determined that the stepping motor 210 has reached the target speed (S102: YES), the control unit 110 executes the speed feedback control of the brushless motor 220 (S103 (second operation phase)). More specifically, the control unit 110 executes speed feedback control for maintaining the rotation speed of the brushless motor 220 at the target speed.

Next, the control unit 110 operates the gear moving mechanism 235 to switch the first power transmission unit 230 to the released state (see FIG. 2B), and releases the connection between the stepping motor 210 and the drive shaft a71 (S104). ..

After that, the control unit 110 turns off the power of the stepping motor 210 that has been disconnected and stops it (S105).

Next, the control unit 110 determines whether or not all the sheets S of the print job have been transferred (S106). When it is determined that the transfer is not completed (S106: NO), the control unit 110 waits until the transfer is completed. That is, the steady state in which the drive shaft a71 is rotated at the target speed is maintained only by the brushless motor 220.

On the other hand, when it is determined that the transfer is completed (S106: YES), the control unit 110 decelerates and stops the brushless motor 220 (S107). More specifically, the control unit 110 gradually changes the control value of the brushless motor 220.

As described above, in the drive control described with reference to FIG. 4 and the like, in the first operation phase (S101) of accelerating the stopped drive shaft a71 to constant speed rotation, the powers of both the stepping motor 210 and the brushless motor 220 are used. , The rotation of the drive shaft a71 is accelerated, and in the subsequent second operation phase (S103 to 105), the power transmission of the stepping motor 210 by the first power transmission unit 230 is canceled, and the drive shaft a71 is operated only by the brushless motor 220. Drive. Hereinafter, the drive control will be described in more detail with reference to FIGS. 6 and 7.

6 and 7 are timing charts for explaining the operation of the stepping motor 210 and the brushless motor 220. FIG. 6 corresponds to the flowchart of FIG. 4, and FIG. 7 corresponds to the subroutine of FIG. 5 relating to the first operation phase. First, with reference to FIG. 6, the entire drive control will be described. FIG. 6A shows the time change of the rotation speed of the drive shaft a71. 6 (b) and 6 (c) show changes in the rotational speeds of the stepping motor 210 and the brushless motor 220 with time, respectively. Further, in FIG. 6B, the period during which the stepping motor 210 is connected to the drive shaft a71 is shown by a solid line, and the period during which the gear moving mechanism 235 is operated to release the connection is shown by a broken line (hereinafter referred to as a broken line). The same applies to FIG. 7 and the like).

(First operation phase)
In the first operation phase from time t10 to t20, the rotation of the drive shaft a71 is accelerated. During this period, both the stepping motor 210 and the brushless motor 220 drive the drive shaft a71, and both accelerate at the same inclination so as to have substantially the same rotation speed on the drive shaft a71.

(Second operation phase)
The time t20 is the timing when the target speed is reached. As shown in FIG. 6B, when the target speed is reached, the connection of the first power transmission unit 230 is started to be switched to the released state. Then, after the disconnection is completed (time t30), the rotation speed of the stepping motor 210 is started to be decelerated and stopped (time t40). Here, the time required for starting from the stop to the target speed (time t10 to t20) is, for example, 50 msec, and the time required from the start of disconnection to the completion (time t20 to t30) is, for example. It is 10 msec.

On the other hand, as shown in FIG. 6C, the brushless motor 220 maintains a constant rotation speed after the time t20.

(Third operation phase)
When the paper transfer is completed (time t50), the control unit 110 starts decelerating the brushless motor 220 and stops the rotation (time t60).

Next, with reference to FIG. 7, the first operation phase will be described in more detail. FIG. 7A is a partially enlarged view of FIG. 6B up to the time t20, and shows the time change of the rotation speed of the stepping motor 210. FIG. 7B shows the time change of the current value of the stepping motor 210. FIG. 7C shows the time change of the control value of the brushless motor 220. FIG. 7D shows the time change of the torque generated in the stepping motor 210. FIG. 7E shows the time change of the torque generated in the brushless motor 220.

When the stepping motor 210 starts accelerating, the current value of the stepping motor 210 in the stopped state is first set to the holding current value (time t1 in FIG. 7B), and a holding torque is generated in the stepping motor 210 (FIG. 7 (FIG. 7). d) Time t1). In the first operation phase in which the holding torque is generated in the stepping motor 210, the control value (duty command value) of the brushless motor 220 is set to a predetermined value (time t2 in FIG. 7C). As a result, a torque smaller than the holding torque is generated in the brushless motor 220 (time t2 in FIG. 7E). This holding torque is maintained for a minute time (time t2 to t20).

After that, the stepping motor 210 is accelerated according to a predetermined acceleration curve (time t10 to t20 in FIG. 7A). During the period in which the stepping motor 210 is being accelerated, the control value of the brushless motor 220 is also increased according to the rotation speed of the stepping motor 210 (time t10 to t20 in FIG. 7C).

As described above, in the present embodiment, in the first operation phase for accelerating the rotation of the drive shaft a71, the drive shaft a71 is driven by using the powers of both the stepping motor and the brushless motor, so that the output torque is improved. The drive shaft a71 can be stably accelerated in a short time.

In particular, in the present embodiment shown in FIG. 7, the stepping motor 210 generates a holding torque, and torque is applied from the brushless motor 220 to the stepping motor 210 that is stopped in the state where the holding torque is generated (time t2 to t10). More specifically, the drive shaft a71 fixed by the holding torque of the stepping motor 210 is in a state where the torque from the brushless motor 220 is applied. If the acceleration of the stepping motor 210 is started in this state, the operation of the stepping motor 210 is assisted by the torque of the brushless motor 220, so that the drive shaft a71 can be accurately accelerated according to a predetermined acceleration curve in a short time. Unlike the present embodiment described with reference to FIG. 7, when the brushless motor 220 is driven to generate torque after the start of acceleration of the stepping motor 210 or at the same time as the start of acceleration, the load of the stepping motor 210 fluctuates greatly and is removed. There is a possibility that a tone may occur, but in this embodiment, such a problem is prevented.

Further, in the present embodiment, in the second operation phase of constant speed rotation, the transmission of the power of the stepping motor 210 to the drive shaft a71 by the first power transmission unit 230 is canceled, and the drive shaft a71 is operated only by the brushless motor 220. It is driving. As a result, power consumption during constant speed rotation can be suppressed. This is because the use of the brushless motor 220 is more efficient than the stepping motor 210 because the power consumption can be reduced when simply maintaining the constant speed rotation. Note that, unlike the present embodiment, if the power of the stepping motor is turned off while the stepping motor is connected, the load may increase, resulting in an increase in power consumption or step-out. In the embodiment, such a problem is prevented.

(Drive device according to the second embodiment)
In the first embodiment, an example in which the first power transmission unit 230 is provided with a disconnection mechanism is shown. In the second embodiment, in addition to the first power transmission unit 230, the second power transmission unit 240 is also provided with a disconnection mechanism. In the following, the parts different from the first embodiment will be mainly described, and the description of the same configuration will be omitted.

FIG. 8 is a schematic view showing a schematic configuration of a drive device according to a second embodiment. The second power transmission unit 240 of the drive device 200 according to the second embodiment includes gears 241, 242, 243, a rotating shaft a4, and a gear moving mechanism 245. The most upstream gear 242 of the gear train meshes with the teeth of the rotating shaft a2 of the brushless motor 220. The most downstream gear 241 is fixed to the drive shaft a71. In the connected state shown in FIG. 8A (or FIG. 8B), the second power transmission unit 240 drives the power of the brushless motor 220 in the order of the gear 242, the rotating shaft a4, the gear 243, and the gear 241. It is transmitted to the shaft a71.

The gear moving mechanism 245 has the same configuration as the gear moving mechanism 235 of the first power transmission unit 230. That is, the gear moving mechanism 245 includes a cam, a drive source for moving the cam, and the like (neither of them is shown), functions as a disconnection mechanism, and has a rotating shaft a4 and gears 232 and 233 fixed to the rotating shaft a4. Moves away from other gears or in the opposite direction. FIG. 8C shows a release state. In this disengaged state, the gear moving mechanism 245 disengages the gear train of the second power transmission unit 240.

(Drive control in the second embodiment)
Next, the drive control of the drive device for driving the transfer roller 171 according to the second embodiment will be described with reference to FIGS. 9 and 10.

FIG. 9 is a flowchart showing a drive control procedure in the second embodiment executed by the control unit 110. FIG. 10 is a timing chart for explaining the operation of the stepping motor and the brushless motor in the second embodiment.

In the second embodiment, the processing of the first operation phase in which the rotation of the drive shaft a71 is accelerated and the subsequent second operation phase of the constant speed rotation are the same as those in the first operation phase shown in FIGS. It is the same, only the third operation phase following the second operation phase is different. Therefore, FIG. 9 shows only the processing of the third operation phase performed after step S106. Further, the timing chart of FIG. 10 is the same as that of FIG. 6 up to the second operation phase (time t0 to t40), and here, the processing after the third operation phase (time t42 to t60) will be described. The algorithm shown by the flowchart of FIG. 9 is stored as a program in the storage unit 120 and executed by the control unit 110.

First, when the control unit 110 determines that the transfer of the paper S is completed (S106: YES), the control unit 110 immediately starts the rotation of the stepping motor 210 (time t42) and accelerates to the target speed (S301). .. At this point, the first power transmission unit 230 is in the released state (see FIG. 8B), the stepping motor 210 is not connected to the drive shaft a71, and no load is applied. The acceleration curve at this time may be set to be the same as the acceleration in the period t10 to t20, but since no load is applied, the acceleration curve is compared with the acceleration in the time t10 to t20 so as to reach the target speed earlier. It may be steep.

When the rotation speed of the stepping motor 210 reaches the target speed, the control unit 110 operates the gear moving mechanism 235 to switch the first power transmission unit 230 to the connected state (see FIG. 8A), and the stepping motor The 210 and the drive shaft a71 are connected (S302, time t50).

Next, the control unit 110 operates the gear moving mechanism 245 to switch the second power transmission unit 240 to the released state (see FIG. 8C), and releases the connection between the brushless motor 220 and the drive shaft a71 (see FIG. 8C). S303, time t50).

After that, the control unit 110 turns off the power of the brushless motor 220 and stops it (S304, time t50 or later).

Further, the control unit 110 decelerates and stops the stepping motor 210 (S305, time t50 to t60). More specifically, the control unit 110 gradually reduces the operating frequency of the stepping motor 210 so that the rotation speed decreases according to a predetermined deceleration curve.

In the drive device 200 according to the second embodiment, in the third operation phase, the power transmission of the stepping motor 210 is switched from the disconnected state to the connected state, and the power transmission of the brushless motor 220 is switched from the connected state to the disconnected state. ing. After that, the stepping motor is controlled to decelerate and stop. By doing so, in the second embodiment, the same effect as that of the first embodiment can be obtained, and further, by controlling the stop by the stepping motor 210 at the time of stopping, the braking amount until the stop ( The amount of rotation) can be controlled with high accuracy. The transport roller 171 that transports paper is particularly useful because it requires highly accurate control of the stop position.

(Modification example)
In the above-described embodiment, an example in which the gear moving mechanism 235 or 245 is used as the connection / disconnection mechanism for connecting / disconnecting the power transmission to the drive shaft a71 of each motor has been described, but the present invention is not limited to this. FIG. 11 shows another example in which a clutch is used as the disconnection mechanism. In the drive device 200 according to the modification shown in FIG. 11A, the first power transmission unit 230 has a clutch 239. The clutch 239 is composed of, for example, an electromagnetic clutch, is provided with a gear 234, and is attached to one end side of the drive shaft a71. The clutch 239 cuts off or connects the power transmission of the stepping motor 210 to the drive shaft a71. As a result, the first power transmission unit 230 is switched to the connected state or the disengaged state.

FIG. 11B is an example in which the clutch 249 is further provided in the second power transmission unit 240. Similarly, the clutch 249 provided with the gear 241 is attached to the other end side of the drive shaft a71 to cut off or connect the power transmission of the brushless motor 220 to the drive shaft a71. As a result, the second power transmission unit 240 is switched to the connected state or the disengaged state.

Even if a clutch is used as the disconnection mechanism as in this modification, the same effect as that of the first and second embodiments described above can be obtained.

(Other variants)
In the flowcharts described with reference to FIGS. 4, 5 and 8 described above, the execution may be performed in an order different from the order shown in these figures. Therefore, this embodiment should not be considered limited to the specific sequence of steps shown in these figures. For example, steps S103 to S105 or S302 and S303 may be executed in parallel at the same time. Further, the method is not limited to the subroutine of step S101 in FIG. 5, and acceleration may be started at a predetermined acceleration at the same time by the brushless motor and the stepping motor at other operation timings.

Further, in the above-described embodiment, the case where the driving device 200 of the present invention is applied to the image forming device 100 and drives the transport roller 171 inside the image forming device 100 has been described as an example. However, the driving device 200 of the present invention may be applied to a post-processing device connected to an image forming device to drive a transfer roller inside the post-processing device.

Further, in the above-described embodiment, the case where the drive shaft a71 of the transfer roller 171 is driven by the drive device 200 of the present invention has been described as an example. However, the drive shaft driven by the drive device 200 of the present invention is not limited to the drive shaft a71 of the transfer roller 171. The drive device 200 of the present invention can also be used to drive a drive shaft for driving the crimp separation mechanism of the transfer roller 171. In this case, for example, a cam is attached to the drive shaft, and the cam converts the rotational movement of the drive shaft into a translational movement.

The means and methods for performing various processes in the image forming apparatus according to the above-described embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. Further, the above program may be provided as a single application software, or may be incorporated into the software of the device as a function of the image forming device.

100 Image forming device 110 Control unit 120 Storage unit 130 Image reading unit 140 Image forming unit 150 Fixing unit 160 Feeding unit 170 Paper transport unit 171 Transfer roller a71 Drive shaft 200 Drive unit 210 Stepping motor 220 Brushless motor 230 First power transmission unit 231 232, 233, 234 Gear 235 Gear movement mechanism 239 Clutch 240 Second power transmission unit 241 242, 243 Gear a2, a2, a3 Rotating shaft 245 Gear movement mechanism 249 Clutch

Claims (7)

With a stepping motor
Brushless motor and
A first power transmission unit that transmits the power of the stepping motor to the drive shaft, and a first power transmission unit that can switch between a connected state in which power is transmitted to the drive shaft and a release state in which transmission is released.
A second power transmission unit that transmits the power of the brushless motor to the drive shaft,
The stepping motor, the brushless motor, and a control unit that controls the first power transmission unit and controls the transmission of power to the drive shaft are provided.
In the first operation phase in which the control unit accelerates the rotation of the drive shaft to a predetermined speed, the control unit transmits the power of both the stepping motor and the brushless motor to drive the drive shaft.
After the first operation phase, in the second operation phase in which the drive shaft is rotated at a constant speed at the predetermined speed, the power transmission of the stepping motor by the first power transmission unit is canceled, and the brushless motor alone is used. Drive the drive shaft ,
In the first operation phase, the current value of the stepping motor in the stopped state is set to the holding current value, the holding torque is generated in the stepping motor, and then the control value of the brushless motor is set to a predetermined value. , The brushless motor is generated with a torque smaller than the holding torque, and then the stepping motor is accelerated according to a predetermined acceleration curve to maintain the control value of the brushless motor constant, or the control value is set to the control value. A drive device that increases according to the rotation speed of the stepping motor. The control unit maintains a state in which power transmission of the stepping motor is released in a third operation phase of decelerating the rotation of the drive shaft, and controls the brushless motor to decelerate and stop the stepping motor. The drive device described in. The second power transmission unit can be switched between a connected state in which the power of the brushless motor is transmitted to the drive shaft and a release state in which the transmission is released.
In the third operation phase of decelerating the rotation of the drive shaft, the control unit switches the power transmission of the stepping motor to the connected state and switches the power transmission of the brushless motor to the released state before the start of deceleration. The drive device according to claim 1, wherein the stepping motor is then controlled to decelerate and stop the stepping motor. The first power transmission unit has a gear moving mechanism for moving at least one gear among a plurality of gears constituting a clutch or a gear train that transmits the power of the stepping motor to the drive shaft. The drive device according to any one of claims 1 to 3, wherein the transmission of the power of the stepping motor to the drive shaft is switched to the connected state or the disengaged state by the clutch or the gear moving mechanism. The second power transmission unit has a gear moving mechanism for moving at least one gear among a plurality of gears constituting a clutch or a gear train that transmits the power of the stepping motor to the drive shaft. The drive device according to claim 3, wherein the transmission of the power of the brushless motor to the drive shaft is switched to the connected state or the disengaged state by the clutch or the gear moving mechanism. An image forming apparatus having the driving device according to any one of claims 1 to 5. The image forming apparatus according to claim 6 , wherein the drive shaft is a drive shaft of a transport roller for transporting paper or a drive shaft for driving a crimping separation mechanism of the transport roller.